The present invention relates generally to an aerial or boom extension system, and more particularly, is directed to a novel extension system that functions with its cylinder in tension.
Numerous types of telescoping booms and aerials have been designed and constructed by prior workers in the art to permit workmen to easily reach elevated heights for such purposes as building construction, fire fighting, tree prunning various electrical construction and maintenance procedures and the like. The present invention relates particularly to improvements over telescoping ladder or boom extension systems of the type which are equipped with a hydraulic cylinder or cylinders for extension or retraction purposes. So far as is known, in all of the presently available extension systems for booms or aerials which function upon use of hydraulic cylinders, the extension is accomplished by a hydraulic cylinder that operates in compression.
In the compression type cylinder system, the cylinder must be strongly designed so that the piston rod will not buckle under the compression forces required to extend a plurality of movable sections relative to a base section. This design concept requires a piston rod of enlarged diameter to provide the required strength, the size of which thereby increases both the weight and the cost of such apparatus. The presently available compression cylinder systems are therefore by their very nature quite massive in structure and relatively expensive in fabrication. Additionally, the weight of the cylinder components adversely affects the capacity of the entire boom or ladder extension system by reducing the power available for lifting and extending a given payload. The present invention seeks to provide an improved structure in the cylinder system which acts to lighten the system components and thereby reduce weight and costs and increase the available payload when utilizing the same power input.